Bukh diesel, manual start, how to

[Gitane]

I posted this link under another forum section, but this is probably the right place for this topic.

I have managed to manually start my Bukh diesel after receiving a tip on how to "decompress" the engine.

I was keen to learn how to do this in case I run out of batteries and really need the engine to get out of trouble.

Here is a short clip on how I got the engine going using the starting handle, although it did take three attempts.

https://youtu.be/IjueyfWDSeQ

 

[pvb]

Just one tiny observation: when using a starting handle, you should never have your thumb on the opposite side of the grip to your fingers. If the engine kicks back, it's easy to break your thumb!

This video shows how to hold the handle correctly - https://www.youtube.com/watch?v=BjLiGqC_YsI

 

[bedouin]

Just one tiny observation: when using a starting handle, you should never have your thumb on the opposite side of the grip to your fingers. If the engine kicks back, it's easy to break your thumb!

This video shows how to hold the handle correctly - https://www.youtube.com/watch?v=BjLiGqC_YsI

I've heard that said many times but does it actually happen? Firstly the Bukh has such a heavy flywheel that it would be pretty difficult for a single firing of the cylinder to reverse all that momentum and secondly if it did the starting handle would be pushed out rather than driven backwards.

Starting even a 2 cylinder Bukh is much harder than a Morris 1100 (or was it 950?) (I know as I tried both and only succeeded in one )

That said when I crank an engine I have my hands beneath the handle and the thumbs on top (and release the compressors on the up stroke) so if it were to kick back it would be into the palm of my hands not the thumbs. Not sure if that is better or worse - could perhaps end up with broken wrists rather than just broken thumbs

 

[RichardS]

Just one tiny observation: when using a starting handle, you should never have your thumb on the opposite side of the grip to your fingers. If the engine kicks back, it's easy to break your thumb!

This video shows how to hold the handle correctly - https://www.youtube.com/watch?v=BjLiGqC_YsI

See posts 25 and 28 of the original thread for the full skinny.

http://www.ybw.com/forums/showthread.php?467215-Another-Bukh-engine-question-Cooling-water-outlet

It is, indeed, only petrol engines you need to worry about.

Richard

 

[afterpegassus]

Only ever managed to start mine when warm with the handle. Certainly needed a lot more grunt than in the video.

 

[bedouin]

and secondly if it did the starting handle would be pushed out rather than driven backwards.

The thread richard references below correctly points out that that bit is nonsense.

 

[Gitane]

The thread richard references below correctly points out that that bit is nonsense.

I am sure engine kick back is a problem on some/most engines.

However, looking at the design of the, whatever the thing you put the handle bar in is called, it has a sloping circular structure inside. This means that when you stop turning the handle and release the decompressor, the engine will, because of the momentum of the flywheel, continue to turn. At that stage the sloping structures inside the thingy will push the starting handle out of the thingy. Assuming you stop turning the handle before you release the compressor, should the engine kickback, it should theoretically not turn the now disengaged handle.


However, having said all that, I don't fancy a broken thumb, so I will take note of the warning and hold the starting handle as described next time I try a manual start.

 

[RichardS]

I am sure engine kick back is a problem on some/most engines.

However, looking at the design of the, whatever the thing you put the handle bar in is called, it has a sloping circular structure inside. This means that when you stop turning the handle and release the decompressor, the engine will, because of the momentum of the flywheel, continue to turn. At that stage the sloping structures inside the thingy will push the starting handle out of the thingy. Assuming you stop turning the handle before you release the compressor, should the engine kickback, it should theoretically not turn the now disengaged handle.


However, having said all that, I don't fancy a broken thumb, so I will take note of the warning and hold the starting handle as described next time I try a manual start.

You're right. As described in the other thread that's why a diesel engine, even if it were to kick back, would not hurt you because you can build up momentum in the flywheel when the engine is decompressed and that momentum will disengage the handle. With a petrol engine it can fire backwards as soon as you approach TDC and are still pushing the handle clockwise. There is no momentum to release the handle so it suddenly flicks backwards.

The same thing can happen with a motorbike kickstart. If you saw a biker with a leg in plaster the standard greeting was "How's the Goldie?", even if you'd never met before.

Richard

 

[forelle541]

Well I broke my wrist starting a Diesel engine a few years ago, actually the scaphoid bone. So I can tell you that a diesel can and will kick back if it decides to.

 

[RichardS]

Well I broke my wrist starting a Diesel engine a few years ago, actually the scaphoid bone. So I can tell you that a diesel can and will kick back if it decides to.

Were you using the decompressor, at least until you built up some momentum? If not, then it's effectively the same as a petrol engine.

Richard

 

[forelle541]

Yes it was a large generator engine and you could not move it through compression without the de compressor.

 

[forelle541]

I think that what happens is that when you close the de compressor leaver the engine bounces on the compression and that is what springs back.

 

[Poignard]

I have had a BUKH engine for 19 years and, until last year when I fitted a second battery, I frequently had to hand start it. It has never kicked back.

 

[RichardS]

I think that what happens is that when you close the de compressor leaver the engine bounces on the compression and that is what springs back.

I have to say that its very unusual for that to happen as diesels nearly always have a large heavy flywheel which once up to speed when de-compressed is not going to kick back on the first revolution, especially when you can usually release the handle even before you release the de-compressor. They can sometimes kick back as they slow down and decide to fire on the last compression but the handle has been thrown well clear by then unless one is pressing it into the ratchet for some reason.

Of course, if you don't build up any momentum in the flywheel then they can bounce back against the first compression if you are still holding the handle when you release the de-compressor.

Richard

 

[bedouin]

I have to say that its very unusual for that to happen as diesels nearly always have a large heavy flywheel which once up to speed when de-compressed is not going to kick back on the first revolution,

Isn't that really the point, you can build up enough energy in the flywheel to carry the engine through the first compression cycle without (much) use of the handle.

 

[pvb]

I think the key point is, as I posted earlier, that to be safe you don't wrap your thumb around the starting handle!

 

[RichardS]

I think the key point is, as I posted earlier, that to be safe you don't wrap your thumb around the starting handle!

See post #9 and don't wrap your wrist around the starting handle.

Richard

 

[afterpegassus]

I have had a BUKH engine for 19 years and, until last year when I fitted a second battery, I frequently had to hand start it. It has never kicked back.

So, did you have a particular technique? Throw one decompressed at a time perhaps?
Doesn't matter how fast I spin the handle, I can't get get over tdc - apart from when warm.

 

[Poignard]

So, did you have a particular technique? Throw one decompressed at a time perhaps?
Doesn't matter how fast I spin the handle, I can't get get over tdc - apart from when warm.

First prime the fuel system using the priming lever on the lift pump.
Then position the starting handle so that when it is descending on the port side of the engine the engine is on a compression stroke. Doing this means my weight, aided by gravity, aided by the momentum of the flywheel, will help get the engine through the first compression stroke.
Then operate the decompressor and turn the engine at increasing speed until it's going as fast as I can do it.
Release the decompressor.

If your engine is worn, a teaspoon of oil introduced into the cylinder gives a temporary increase in compression and helps starting.

Starting is always easier if the air being drawn in is warm. A preheater (obtainable from BUKH Ltd) is worth fitting especially for winter use. Installing it is an easy DIY job. Or wrapping the air intake in rags soaked in boiling water helps.

 

[seumask]

Update on my post on the previous thread.
I was at the boat this weekend winterising the DV24 and the temp was around 6C. I thought I'd try and start the engine by hand in preparation for the oil warm up. I help open the compression lever with a piece of 3mm chord led to underneath my shoe. I got winding for around 8 seconds and let the chord go. Nothing happened. So I tried again and this time got going a little faster and I wound for around 10 seconds before letting go and hey presto the engine fired and ran as usual. Just goes to prove I can start it by hand still.
A couple of observations : The starting handle is in my hand detached from the engine as I let the decompression lever go, this seems to occur naturally and I don't suffer from any worries about kick back, the flywheel is heavy and I simply cant turn the engine over if the decompression lever is not activated.
I think its a wonderful engine as I can start it by hand and I'm a fairly small averagely strong person.